• Journal of Ocean Engineering and Technology
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• v.34 no.4
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• pp.272-276
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• 2020

This paper presents an optimization process for a catamaran hull form. The entire optimization process was managed using the CAD-CFD integration platform CAESES. The resistance of the demi-hull was simulated in calm water using the CFD solver STAR-CCM+, and an inviscid fluid model was used to reduce the computing time. The Free-Form Deformation (FFD) method was used to make local changes in the bulbous bow. For the optimization of the bulbous bow, the Non-dominated Sorting Genetic Algorithm (NSGA)-II was applied, and the optimization variables were the length, breadth, and angle between the bulbous bow and the base line. The Lackenby method was used for global variation of the bow of the hull. Nine hull forms were generated by moving the center of buoyancy while keeping the displacement constant. The optimum bow part was selected by comparing the resistance of the forms. After obtaining the optimum demi-hull, the distance between two demi-hulls was optimized. The results show that the proposed optimization sequence can be used to reduce the resistance of a catamaran in calm water.

• Journal of Korean Foot and Ankle Society
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• v.7 no.1
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• pp.21-29
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• 2003

Purpose: The purpose of this study is to review clinical and radiologic changes after arthroscopic operation without bone graft for osteochondral lesion with subchondral cyst on the talus. And we compared the results with those without cyst. Radiologic changes were also observed. Materials and Methods: Arthroscopic microfrature or abrasion arthroplasty was performed on 10 caeses of osteochondral lesions with subchondral cyst and 20 cases without cysts. Preoperative and postoperative symptoms were evaluated by Ankle-Hind foot scale of AOFAS and the score of two groups were compared(t-Test : Paired Two Test for Means). Radiologic evaluation was performed after operation on patients with osteochondral lesion with cyst. Results: On patients of osteochondral lesion with subchondral cyst on talus, there was clinical improvement compared to the preoperative status and compared to patients without cysts(P=0.01) after arthroscopic operation. We could get increase of density and decrease of size of cystic lesion on plain film with time passage. Conclusion: We report 10 cases with osteochondral lesion with subchondral cyst on talus which resulted in clinical and radiological improvement after arthroscopic microfracture or abrasion arthroplasty without bone graft.

• Journal of Chest Surgery
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• v.44 no.1
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• pp.25-31
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• 2011

Background: Mature autogenous arteriovenous fistulas have better long term patency and require fewer secondary interventions compared to arteriovenous prosthetic graft. Our Study evaluated vascular patency rates and incidence of interventions in autogenous arteriovenous fistulas and grafts. Material and Methods: A total of 166 vascular access operations were performed in 153 patients between December 2002 and November 2009. Thirty seven caeses were excluded due to primary access failure and loss of follow-up. One group of 92 autogenous arterioveous fistulas and the other group of 37 arteriovenous prosthetic grafts were evaluated retrospectively. Primary and secondary patency rates were estimated using the Kaplan-Meier method. Results: The primary patency rate (84%, 67%, 51% vs. 51%, 22%, 9% at 1, 3, 5 year; p=0.0000) and secondary patency rate (96%, 88%, 68% vs. 88%, 65%, 16% at 1, 3, 5 year; p=0.0009) were better in autogenous fistula group than prosthetic graft group. Interventions to maintain secondary patency were required in 23% of the autogenous fistula group (average 0.06 procedures/patient/year) and 65% of prosthetic graft group (average 0.21 procedures/patient/year). So the autogenous fistula group had fewer intervention rate than prosthetic graft group (p=0.01) The risk factor of primary patency was diabetus combined with ischemic heart disease and the secondary patency's risk factor was age. Conclusion: Autogenous arteriovenous fistulas showed better performance compared to prosthetic grafts in terms of primary & secondary patency and incidence of interventions.